In the example described in document FR-2,670,440, the thermal engine comprises an output shaft that drives the motive part of a variable transmission, such as a variable speed drive, and whose transmission receiving part is connected to the motive axle of the vehicle. The output shaft carries, between the thermal engine and the variable speed drive, an electric machine connected to an electric battery and two clutches, a first clutch between the thermal engine and the electric machine, and a second clutch between the electric machine and the variable speed drive.
When the vehicle is to be driven with a high torque over a wide speed range while limiting exhaust gas and noise generation, as in an urban site, the electric machine is preferably used for driving the motive axle of the vehicle.
On the other hand, for uses where a high engine driving power and a wide operating range are required, the thermal engine is used for driving the motive axle and thus providing displacement of the vehicle.
Although satisfactory, this drive system however involves some significant drawbacks.
In fact, when only the electric machine is used to drive the vehicle, it must have a sufficient torque and/or power for driving the vehicle as well as overcoming all the resistances (inertia, friction, . . . ) of the variable transmission. Furthermore, during vehicle braking operations, part of the energy released thereby is consumed by the variable speed drive and only another part of this energy is recovered, then converted by the electric machine.
If a mechanical gearbox is used instead of the variable speed drive, it is essential to change the gear ratio in order to recover the braking energy. It is therefore necessary to disengage the motive axle, which causes a break in the motion transmission and an interruption of the braking energy recovery.
The present invention aims to overcome the aforementioned drawbacks by means of a simple drive system that requires no complicated control devices for the various uses of the system.